The field of pathology is evolving so as to embrace two disciplines, one of which is subsumed into the other: diagnosis and prognosis. Each is a medical discipline in which biochemistry and molecular biology play increasingly important roles, allowing innovations in traditional diagnosis as well as reliable protocols for prospective outcome prediction. If a diagnostic test or assay, or "diagnostic," provides specific information regarding the nature of a disease, a "prognostic" test or assay provides specific information regarding the outcome of that disease--but within the conceptual confines of the original diagnostic. Properly developed prognostics allow a determination to be made in advance, with statistically significant and surprising accuracy and precision, whether a given drug or active agent, or therapeutic protocol including surgery or other treatments, will be effective to inhibit or to overcome the disease or condition in question.
In a very real sense, prognostics give a wider scope of benefit than traditional diagnostics do, even though they fall within the diagnostic field in general. Before the advent of the field of prognostics, various therapies had to be attempted sequentially based upon general guidelines developed from overall patient population data, but in many cases these general guidelines had disappointing predictive value with respect to any given patient or any given treatment. Against this backdrop, it can be seen that a prognostic can yield not only scientific and medical value but also both a heretofore-elusive humanitarian advantage (quality of life) as well as significant economic benefit (cost effectiveness). With a prognostic, for example, a given patient need not endure a given treatment simply to ascertain whether that treatment is likely to be effective. A properly designed prognostic gives a health care provider information about risk category and likelihood of survival, which in turn assists in determining appropriate therapy. It is easy to appreciate the particular utility of a prognostic in the challenging area of cancer treatment, where the benefit of a patient's not having to endure unnecessary treatment may be the greatest for any disease.
Cost savings also become significant when medical practitioners are provided with a tool by which to predict, for a given patient, whether a given therapy will be effective--because therapies unlikely to be effective are generally passed over at the outset. (Alternatively, the prognostic's predictive utility may appropriately identify patients for inclusion in the prospective investigation of novel treatments.) When therapies unlikely to be effective are skipped altogether, the costs (and waste) involved in the failed therapy are also avoided. Neither the cost nor the health benefit of avoiding likely-to-be-futile therapies should be underestimated. The improvement in morale in any patient who knows his chosen therapy is predictably effective as to him or her individually itself contributes to the successful therapy in a manner analogous to the placebo effect.
In general, the best prognostics are those in which the particular biochemistry or molecular biology of biopsied tissue--or, alternatively, of blood or body fluids--can be assayed and quantitated to yield an objective outcome likelihood. Such biochemical "markers" might be anything, including but not limited to catabolytes, anabolytes, enzymes, hormones, other expressed peptides or proteins, distinct saccharides, or any other distinctive biomolecule. As a design consideration, the theoretically best biochemical marker for a prognostic would be one or more uniquely expressed peptides or proteins, because these could be readily identified (and quantitated) by corresponding monoclonal antibodies. The ideal cancer prognostic would therefore involve the identification of a critical threshold expression level for one or more unique peptides or proteins having prognostic significance. Such an assay could be performed with existing laboratory reagents and equipment, using standard monoclonal antibodies and optical-counting quantitation techniques, and would therefore be inexpensive as well as accurate and precise. Because the assay would be undertaken to ascertain expression levels in a given patient, the results would have prognostic value specific to that patient.